Reducing aerial oxidation of photographic developers



many developers,

esame! TET QFFlCE UCIN G AERIAL OATION 619E? PEQ'EOGC DEVELOPERS =1 andWesley '1'. Hanson, Jr., h

gnors to Rochwter, N. Y

man Kodak'floma corporation of, New

i No Draw. Appiimtlon Member 9, 1939,

S No. 308,464

This invention relates to photographic developers and particularly to amethod and agents for reducing aerial oxidation of photographicdevelopers. I

In some photographic developing machines, the developer solutions areagitated by air. This aeration sometimes oxidizes more of the de-'veloping agent than the actual development process itself and thuscauses additional expense due to exhaustion of the developer, as well astion of the solution. Soluble sulfltes, such as sodium sulfite, arecustomarily added to developing solutions with the purpose of preservingthe developer and preventing aerial oxidation, but the use of s'ulflteis objectionable in particularly color-forming developers, in whicharomatic amino developing agents are used. 4

It is, therefore, an object the'present invention to provide a novelmeans for preventing aerial oxidation of photographic developers,"especially color-forming developers. A further object is to provide ameans for reducing the amount of sulflte used in color-forming photographic developers.

These objects are accomplished by the addition or small amounts ofhydroquinones to developins solutions containing aromatic aminodeveloping agents, orv in general the addition of reducing agents havinga. higher solution reduction potential than the developer in questionbut which are not strongly adsorbed to the grains in the emulsion and,therefore, take only a very small part in the actual developmentprocess.

Reducing agentsiwhich may be used ior this purpose include hydroquinone,hydroquinone monosulionate, toluh'ydroquinone or similar dihydroxycompounds. When these compounds are added to an amino developersolution, the

oxidation due to air agitation will affect the. hydroquinone or otherreducing agent to a much greater extent than the amino developer due tothe higher solution reduction potential oi the hydroquinone or otherdihydroxy compound. However, since the amino developer is much morestrongly adsorbed tothe silver halide grains than the hydroxy compound,the amine compound will be more active in the development process andits oxidized form will still be available for torming a dye image withany coupler that is presout.

any reducing agent whose electrochemical. solusome dimculty incontrolling the developing ac- Our invention, therefore, resides in theuse of I the developing the solution.

tains one or more substituted or tacked and oxidized by air.

The following examples mentioned.

1 Example 1 Diethyl-p-phenylenediamine grams.. 2 Sodium sulfite -..do 5Sodium carbonate do Potassium bromide -do 5 o-Naph do 1 Sodium hydroxidedo 1.5 Hydroquinone do 0.3 Water to 1000 Example 2Dietlrvl-p-phenylenediamine ....grams-.. 2 Sodium sulflte do..- 5 Sodiumcarbonate do..--.. 20 Potassium bromide ...do--.. 5

00 2,3,4-triclfloro-naphtho1 do '1 1 Sodium hydroxide ..--.do 1.0Hydroquinone monosulionate -..-..-do. 1.0 Water to 1000 Y a Example 3-Dimethyl-p-phenylenediamine --grams. 3 Sodium sulilte do.. 0' Sodiumcarbonate .do.-'.- 20 Potassium bromide .do- 5 o 4-chloro-o-phenylphenol-.. --.do 1 Sodium hydroxide do..--- 1.0 Toluhydroquincne.'...do--.-- 0.2 Water to or 1000 lmmple 4 Diethyl-p-phenylenedisminegrsms 2 Sodium sulflte ...do.... 40 Sodium carbonate do 20 Y Potassiumbromide do. 5

5 u-rlaphtho do 15' Sodium hydroxide.- ....-do-.. 1.5 Hydroquinonemonosulionate do 1.0 Water to 1000 The dihydroxy reducing-agents used inthe tionreduction potential is higher than that of develop'ermgy nd invarying t; t

agent butwhose photographic reduction potential is less than that oi thedeveloping agent to decrease aerial oxidation of the developer withoutgreatly affecting the photo- 5 graphic activity of larly propose to usethese reducing agents with developing solutions in which the developercon-- unsubstituted amino groups and where the developer is to be usedunder conditions such that it is readily at- We particuv illustratedeveloping solutions containing reducing agents of the type colorforming developers containing from 1 to 5 grams of developing agent perliter of developing solution. The amount of added dihydroxy compound mayvary from about 0.1 gram to 1.0 gram per liter.

In many cases the dih'ydroxy reducing agents, besides preventing aerialoxidation of the developer, have an additional-beneficial efiect inretarding the formation of a general dye stain which the colordeveloping agent is not subject to aerial oxidation, comprisinga primaryaromatic amino coupling developing agent, a coupler anda hydroquinone.

2. A color-forming photographic developer in which the color developingagent is not subject to aerial oxidation, comprising aparaphenylenediamine developing agent, a coupler and a hydroquinone.

3. A color-forming photographic developer in which the color developingagent is not subject to aerial oxidation, comprising aparaphenylenediamine developing agent, a coupler and hydroquinone.

4. A color-forming photographic developer in which the color developingagent is not subject to aerial oxidation, comprising aparaphenylenediamine developing agent, a coupler and hydro quinonemonosulfonate.

RALPH M. EVANS. 1 WESLEY T. HANSON, JR.

